The present invention generally relates to a device for testing an electronic device, and more particularly to a test device suitable for measuring a propagation delay time of a device such as a semiconductor device and an intermittent change of an output signal. Further, the present invention relates to a method for testing an electronic device. Furthermore, the present invention relates to a semiconductor device having the test device.
Recently, a semiconductor device such as a memory device has a large capacity and operates at very high speed. Therefore, it takes a very long time to obtain data for evaluating performance of a semiconductor device. Generally, an input pattern corresponding to a test condition is supplied to a device to be tested, and it is determined whether the device under test is good or bad on the basis of output data derived therefrom. Then the test condition is altered and a corresponding input pattern is supplied to the device under test. In order to obtain data sufficient to evaluate the device under test, the above-mentioned procedure is repeatedly carried out.
The propagation delay time of a device is one of the most important factors particular in a memory device. The propagation delay time of a device is measured as follows. An input pattern is supplied to a device to be tested. It is noted that generally an input pattern is not used for measuring only the propagation delay time but used for measuring various characteristics of the device. Then it is determined whether the device under test is good or not. If the result is not good, the device under test is supplied with a different input pattern directed to obtaining the result of 'good'. Then it is determined whether the device under test is good or not. In this manner, different input patterns are repetitively supplied to the device under test, and the propagation delay time thereof is calculated on the basis of the results obtained for the respective test conditions (patterns). It can be seen from the above description that it takes a very long time to obtain the propagation delay time. Further, in order to find an intermittent change of the output signal derived from the device under test, different input patterns must repetitively be supplied thereto.